Cannot render, because of too many faces
Lower your subdivision modifier from 6 to 3 (at most: 3).
Please check double geometry on all of your models (even simpler ones) There could be intersecting double faces. Enter edit mode, press F3 (to search) or Spacebar (user preferences to set spacebar to search) and while in edit mode, type "remove doubles".  You´ll get notification on how many edges were cleaned.
Also check your materials don't contain special characters, this is another reason why in the process of "pre-processing" before rendering the render crashes. Make sure spaces are appropiate (use a "." or "_" to separate numbered versions of the materials or the meshes)
6 millions of polygons shouldn´t be a big deal if you have 12GB+ of Ram. Also switch to CPU rendering only. Do not process with EEVEE. Use Cycles. /// I´ve render 15 million polys on Cycles on CPU due to the lack of processing on 12GB VRam for GPU on my Titan X card. So you may as well play safe on the Cycles CPU render part thus answering this question.


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BFCT_Schiller